Welded joint



1966 P. J. RIEPPEL ETAL 3,236,547

WELDED JOINT Original Filed July 5, 1959 Perry J. Rilppel ATTORNEYUnited States Patent Office 3,236,547 Patented Feb. 22, 1966 3,236,547WELDED JOINT Perry J. Rieppel, Worthington, and Glenn E. Faulkner andJerome W. Nelson, Columbus, Ohio, and Harry C. Cook, Orange, N.J.,assignors, by direct and mesne assignments, to Esso Research andEngineering Company, a corporation of Delaware Original application July5, 1959, Ser. No. 825,159, now Patent No. 3,084,246, dated Apr. 2, 1963.Divided and this application Aug. 14, 1962, Ser. No. 216,792

4 Claims. (Cl. 285286) This application is a division of Serial No.825,159, filed July 5, 1959, now Patent Number 3,084,246. The parentapplication was concerned with a process for forming welded jointsbetween pipes and other metal shapes and also with apparatus forcarrying out such a process.

The present invention relates to an improved welded joint. It relatesmore specifically to circumferential welds used particularly inpipelines and analogous structures. In its broader aspects, it can beused in out-of-position welding and in some of its aspects it can beapplied in joining the edges of flat or curved plates to form buttjoints in various positions.

As one of its more important applications, the weld will be describedespecially with reference to welded joints in steel pipe, such as isused in pipelines for transmission of natural gas and petroleumproducts. The invention, of course, has other applications as well.

In the prior art, various suggestions have been made for automatic orsemiautomatic welding of butt joints in pipes and other structures.Generally speaking, however, the prior proposed automatic apparatus andmethods are too slow and have not been satisfactory or have at leastrequired considerable manual work or large, cumbersome auxiliaryequipment to supplement the machine welding. As a general rule,pipelines have been welded by abutting the pipe ends, previouslymachined to a bevel which forms a groove to be filled with weldingmaterial. This is usually done by clamping the joint internally orexternally to hold the pipe sections in proper abutting relation for thewelding operation and applying the welding material by means of amanually controlled electric arc. The weld metal in the prior artprocess is applied in small increments to fill the V-groove of about 60to 75 angle, this angle being determined when the pipe ends are machinedprior to assembly in the pipeline. This type of Welding has usually beenaccomplished first by tacking with small pools or globlules of moltenweld metal and is then carried on piecemeal in a series of manualoperations. It requires considerable operative skill as well as muchtime and material to do an acceptable job. Some of the welds made bysuch prior methods tend to be rough and uneven in appearance, and maycontain cavities, flaws and other faults.

Primary objects of the present invention are to provide a welded jointwhich can be made rapidly, especially in large pipes which cannot berotated, by forming carefully controlled, uniformly sized gaps or spacesbetween the parts to be welded and then filling these gaps. Anotherobject is to provide a Welded joint which has been evenly filled in asingle pass operation. Another is to achieve a welded joint having ahigh degree of uniformity in weld quality and strength and having nodeformities of the joint due to shrinking and other forces as thewelding is being accomplished.

Specific objects are the following, although the invention is notlimited thereto, as indicated above:

(A) To provide a satisfactory single pass welded joint especially inplate and pipe of A to inch thickness in all positions, eg, inpipe-welding a welded joint made uniformly in a single pass at the top,sides and bottom of a nonrotated pipe.

(B) To provide a welded joint having an unusually narrow cross sectionalwidth, usually produced by a single pass operation, where the actualjoint (or gap) depth to width ratio is from about 3 to 7:1 (preferably4.5 to 6.511), and where the fusion zone depth to width ratio is of thegeneral range of 2 to 1 or more.

(C) To provide a welded joint of unusual but highly desirable fusionline geometry, especially for single-pass welds. The welded joint ismade by using continuously fed welding wire. The fusion zone narrowsunder the wire burn-01f position but flares out at the root due tosuperheated metal under the arc, thus melting back at the root edges;this ensures good root fusion.

(D) To provide an efficient and economical welded joint which can beformed by a welding action obtained by the proper combination of Weldingvariables (traverse rate, weld wire feed, gap width, electric potentialand current, etc.) in a well controlled and substantially automaticprocess.

(E) To provide a welded joint having an unusual texture and highstrength which is made by an essentially single pass operation in adeep, narrow, vertical, or perpendicular walled gap.

Still more specific objects will appear from a detailed description ofthe welded joint which follows:

The welded joint may be used for straight or flat welds of abuttingmembers, e.g. joints or seams in flat and curved plates as well as forwelding together the ends of adjoining pipe sections. Flat or curvedplates and sheets may be welded in various positions and from variousdirections, vertical, horizontal, overhead or otherwise.

The welded joint of the present invention has the important advantage ofwide flexibility. It can be prepared in high quality by the use ofreasonable amounts of equipment at rates which can keep up with highspeed pipe laying practices in the field and at substantially reducedcost. The joint consistently has adequate tensile strength andductility, equivalent to or greater than that of the basic pipe metals.It can be made by using smaller amounts of welding rod or wire and by aprocess which will more easily protect it from variations in amounts ofwelding rod or wire and by a process which will more easily protect itfrom variations in weather and other ambient conditions than prior artmethods.

Referring now to the drawings,

FIGURES 1 and 2 are sectional sketches showing important details orcritical dimensional relationships in welds of the type underconsideration.

FIGURES 3, 4, 5 and 6 show diagrammatically specific aspects andmodifications of the welded joint as applied to circumferential or girthwelds.

FIGURE 7 is a detailed fragmentary sectional view of a finished weldtypical of those included in the present invention.

In FIGURE 1, the space between the pipe ends has been preciselydetermined, e.g. where cutting is used the joint has been cut throughcleanly and the weld must fill a uniform (in width) gap from bottom totop. When this gap g is carefully controlled in width and uniformity,

an essentialy smooth bottom and top surface may be produced. As the gapis filled, the molten weld wire, and metal which is melted off the pipeends by the heat of the arc, fuses with the pipe progressively asindicated at W The heat of the arc is of greatest intensity around theend of the wire W, about the middle of the pipe wall thickness.Adjoining pipe wall metal is fused here and flows inwardly and outwardlyto melt the root edges of the pipe. This gives the characteristic weldcross section of this joint which is a distinctive and important featureof the present invention.

Where the spacing of smoothly finished pipe end sections can beaccurately controlled and when they can be adequately clamped topreserve an accurate space between the butt ends, cutting is notnecessary. It must be emphasized, however, that the width of the gap allaround the pipe must be held within close tolerance limits, e.g. limitsof 0.003" to 0.005" plus or minus, all the way around the pipecircumference or good welding cannot be accomplished by single passoperation. If maintenance of gap tolerance cannot be effected by simpleclamping, then the cutting must precede the welding to obtain firstquality single pass welds.

Referring to FIGURE 2, the flow of metal in a counterclockwise weldingtraverse is shown. The wire W is fused and forms, together with metalmelted from the pipe, the pool P, which tends to sag in a meniscus asindicated at S However, the metal adjoining the weld extracts heat fromthe .pool very rapidly as the welding arc moves on, causing shrinkage.The middle part of the pipe wall thickness conducts more heat away thanthe portions near the inner and outer surfaces, but the whole moltenmass shrinks as it cools and solidifies. This shrinkage, plus thesurface tension of the sagging metal meniscus, tend to straighten up theinner surface, as indicated at S Hence, a substantially flush surface isformed inside the pipe. The corner fusion at the root or inside surfaceof the weld is a particularly important feature. See FIGURE 7. It is dueto reduced conduction by the pipe material of heat away from the jointas compared to conduction at the middle of the wall thickness.

In practice, the welded joint may be made in several different ways.Under some conditions, it is preferred first to tack the abutting pipeends together as shown in FIGURE 3 at 320. Tacking may be accomplishedalso with spaced welded connections between the abutting ends by meansof bridging bars 322, attached as indicated in FIGURE 4. These hold thegap width constant despite forces set up by shrinkage of the mainwelding material W see FIGURE 1.

The production of the full welded girth joint may also be accomplishedin two major operations as shown by FIGURES 3 to 6, especially FIGURES 5and 6. In a typical operation, the cutting wheel 141 is first swung intocontact with and cuts through the wall thickness the joint at the top ofthe pipe. The cutter is then rotated down one side through approximately180 around the pipe. Assume, for example, that the joint is first cutaround the left half of FIGURE 5 and is subsequently welded. This isaccomplished by first swinging the cutter 141 into operation to cutthrough the pipe wall thickness, and then the cutter is movedcounterclockwise from top to bottom; secondly, the welding unit isbrought into operation and rotated, also downwardly, from the top incounterclockwise direction to provide the shaded welded joint wj abouthalf way around the pipe as shown at the left of FIGURE 5.

Referring now to FIGURE 6, the weld is completed by first bringing thecutter down in the approximate position to cut through to the line m, pof FIGURE 6.

and then swinging it clockwise, while cutting, from point in to point n.This operation, it will be observed, rounds out an arcuate cut or rampindicated at p and ends by leaving a smooth arcuate ramp surface q atthe bottom.

These ramp surfaces p and q are ideally suited for the second half ofthe weld since the weld metal flows in smoothly at the top; and as thewelder swings to the right or clockwise, the joint is filled in such amanner that gravity assists in obtaining smooth flow. At the bottom asthe weld is finished gravity tends to flow the molten metal along thesurface q so as to form a flawless weld in the two operations. Bycontrast, voids tend to be formed as indicated at r and s, FIGURE 5, ifthe end portions of the first half circumfgerence weld are not cut outto put them in workable shape.

FIGURE 7 shows an example of the cross section of a very good weld. Evenwith the fusion of the adjoining pipe metal, the whole weld still isvery narrow; it has a depth to width ratio of about two to one. Suchconfiguration not only minimizes use of welding wire but gives strongsmooth joints of execellent quality.

In contrast to other welded joints, the present weld is made in a singlepass to give an excellent weld cross section. Sections taken from actualwelds show the characteristic shape for the weld itself and the heattreated area adjoining as FIGURE 7 shows. High speed motion pictureswhich have been taken show that the heat of the are apparently reachesits greatest intensity about the middle of the wall thickness, where theconsumable electrode wire burns otf. Wall fusion on both sides, plus themolten wire, provides the superheated molten pool of weld metal whichthe force of the arc pushes inwardly as well as laterally. Thissuperheated Weld metal fuses back the inner wall or root edges to givethe weld cross section a characteristic flared shape at the inner wallwith a narrower waist portion a, FIG. 1, or a, FIG. 7, in between.Ideally, a generally similar shape rv is achieved at the outer wallsurface, as shown in FIG. 7, but the flared root weld rw, FIG. 7, is ofgreater practical importance than the similar structure rv at the top oroutside of the wall. The heat of the weld also heat-treats the metal ofthe pipe wall to give the generally rectangular penumbra effectadjoining the actual weld on both sides. This highly desirable weldformation is a superior feature of the invention.

It will be understood that many variations may be made in dimensions andother factors indicated above so long as their proper interrelationshipsand combinations are observed. It is intended to cover this and otherobvious alternatives as broadly as possible, within the limits of theprior art, by the following claims.

We claim:

1. As an article of manufacture, a pair of metal pipe sections ofessentially similar diameters and wall thickness, joined by fusedweldment having a relatively wide weld cross section at the middle ofthe wall thickness, a flared cross section at the inner wall, and anarrower cross section than either the middle or the flaredcrosssections at a point between said middle and said inner wall, saidfinished joint being substantially flush with the inner pipe wall.

2. Article according to claim 1 wherein the weld area is bounded by aheat treated area which is generally of rectangular cross sectiontransverse to the line of weld wherein the fused weldment has a widthless than the pipe wall thickness.

3. A pair of metal members having end surfaces of substantially equalthickness, said surfaces being flat and planar and disposed in oppositerelationship in parallel closely adjacent planes to form a weldmentreceiving gap and a weldment joining said members together and fillingsaid gap, the central portion of said weldment being fused more deeplyinto each of said members than at other points in the weld, saidweldment also having a flared outer portion at at least one boundary ofthe original plane surfaces which is wider than the original Weldrnentreceiving gap, and a portion on each side of the central portion whichis narrower in cross section than either the center or said at least oneouter portion, the

5 6 Weldment also being substantially flush with original sur- 1,615,6861/ 1927 Egschholz 219137 faces of the members at said flared outerportion. 1,975,495 10/ 1934 Armacost 285-286 X 4. A pair of metalmembers having a weldment ac- 1,980,561 11/1934 Wagner 285-286 X cordingto claim 3 wherein there is a flared outer portion 2,043,952 6/ 1936Efield 29498 X at both surfaces. 5 2,079,265 5/ 1937 Trainer 219-60 X2,141,021 12/1938 Rooke et a1 29497 References Cited by the Examiner2,405,542 8/ 1946 Wassell 285-22 X UNITED STATES PATENTS FOREIGN PATENTS1,158,307 10/1915 Schmid 285286 X 4 3 3 1 Gmt Britain, 1,457,183 5/1923Mitchell 285-489 10 1,599,927 9/1926 Stresau 285-22 X CARL W. TOMLIN,Primary Examiner.

1. AS AN ARTICLE OF MANUFACTURE, A PAIR OF METAL PIPE SECTIONS OFESSENTIALLY SIMILAR DIAMETERS AND WALL THICKNESS, JOINED BY FUSEDWELDMENT HAVING A RELATIVELY WIDE WELD CROSS SECTION AT THE MIDDLE OFTHE WALL THICKNESS, A FLARED CROSS SECTION AT THE INNER WALL, AND ANARROWER CROSS SECTION THAN EITHER THE MIDDLE OR THE FLARED CROSS-